Coated mold and method of molding concrete



June'15, 1943. F. A. WILLIAMS COATED MOLD ANDMETHOD OF MOLDING CONCRETE Filedgm 25. 1940 I l I I r I I I I 1 I I r 1 I 1 r Irrg Patented June 15, 1943 Mr s'r're with? Q i i;

coarse Morin sun Mnrrron er Moraine concan'ra Francis A. Williams, 'ficrento, Ontario, Qanada Application August 23, 1940, Serial No. 353,820

2 @iaims.

ter becomes sufliciently still? to maintain its shape without the aid of the mold or form.

l have discovered that by forming the mold or form of a material having certain characteristics, or by lining or coating the mold or form with such material that an unexpected and valuable result is obtained in the. surface finish of the concrete, namely, that the concrete has a glossy or glazed surface which is substantially impervious to moisture and which is very similar to a glazed tile or porcelain enamel finish The invention is hereinafter more specifically described and is illustrated in the accompanying drawing in which Fig. l is a cross section of a concrete plate or slab constructed in accordance with my invention;

EL. 2 a vertical section of a simple form of I apparatus for carrying out the invention; and

Fig. 3 a plan view of the same.

In the drawing like numerals of reference in= dicate corresponding parts in the difierent Referring to Fig. l, A indicates a concrete slab or plate which may be of any size or thickness depending on the purpose for which it-is intended. The slab or plate may be of uniform texture throughout its mass, but for the sake of economy or other reasons it will usually have its rear portion formed of a difierent mixture than the face portion thereof.

The slab or plate is made from an ordinary wet mixture of cement and aggregate, except that for the face portion the mixture will be of a character and color to suit the requirements of the particular purpose for which the structure is required.

The facing material-is placed in a mold or form 2, which is adapted to be rapidly vibrated on a suitable support 3, by means of any suitable actuating mechanism such, for example, as the crank mechanism ti. By rapidly agitating the form 2, the facing material is firmly compacted and the backing material is then positioned over the facing material and this is then compacted by agitation in a similar manner. It will be understood, of course, that the form may be stationary and-the compacting of the concrete may be obtained by agitating or manipulating the concrete on or in the form.

The color of the facing will, of course, depend on the materials employed, a wide range being available.

Concrete, of course, has a tendency to adhere to the moldor form surface, and therefore considerable care has to be taken in the choice of the mold or form facing with which the concrete contacts.

To obtain the glossy or glazed surface finish desired, it has been found that it is very important that the surface moisture be not allowed to escape into the form from the face side of the structure, or air come in contact with said face side, and the mold or form therefore is provided with a lining or coating of a material which 'is non-absorbent of moisture, which has substantially no bonding aifinity with the concrete, and which is substantially unaffected by the concrete.

This lining or coating is allowed to remain in contact with the surface of theconcrete until the latter has set and hardened sufiiciently to retain enough of the fine surface particles to give the desired gloss or glaze, and it is found that the more the hardening of the concrete has advanced before the lining or coating is removed,

- the higher the gloss the finished surface of the I concrete will have.

It will be apparent, therefore, that if a medium gloss is required, the lining or coating will'be removed sooner than if a full gloss is required.

It has been found that with ordinary concrete a partial gloss is obtained if the lining or coating is left in contact with the concrete for twentyfour hours, and the gloss is heightened by leaving the lining or coating in place for longer periods up to that degree of hardening which will ensure that the fine particles of the surface will remain in undisturbed position and so give thesurface a light reflecting, quality similar to polished granite or glazed porcelain. Under average conditions, a quite high gloss. is obtained,

in thecase of ordinary concrete, by allowing the lining to remain in place for approximately .72 hours.

As'statecl above, the mold or form itself may be made of a material having the above characteristics of being non-absorbent of moisture, non-bonding with the concrete and non-affected by the concrete itself, but the preferred method will usually be to provide that part ofthe form with which the front of the finished structure contacts with a thin lining of suitable material in sheet form, or it may be applied as a liquid by a dipping, brushing or spraying process. This lining .or coating is indicated by the numeral 5 form by Goodyear Rubber Co. under the trade name Pliofilm.

It is found that by interposing Pliofilm" sheeting, or other material having similar characteristics, between the concrete and the mold and allowing the sheeting to remain in contact with the concrete face until the latteris substantially 'hardened, the surface of the concrete retains a finish very smooth and hard, similar to the finish of glazed tiles or porcelain enamel. The form sheeting or coating, beingnon-absorbent and relatively airtight, does not allow the fine par- I ticles of the surface to dry out faster than the body concrete and this sheeting or coating having no bonding affinity for concrete does not attach to itself the fine particles of the surface, and therefore its removal does not roughen the surface, but leaves it' unbroken and glassily smooth whether the surface be level or uneven, with its natural light reflecting and water resisting qualities unimpaired.

The terms non-bonding and having no bonding affinity for the concrete," are used to indicate that the lining or coating may be readily separated from the concrete when the latter has cured without pulling away any of the concrete surface. applied to freshly placed concrete and immediately pulled away, some moisture together with some surface material carried thereby will adhere thereto, but as the concrete becomes hard ened the tendency of the surface material to lift decreases as the hardness of the concrete increases, until when the mass is suificiently hard, there is no pulling of the surface 'when the sheeting or form is'removed.

A sheeting or coating of the nature describedv has a very smooth surface, and being unaffected by the concrete facing material, the latter may It will be apparent that if sheeting is v readily shift around under agitation to form a very compact layer of material immediately adjacent the lining. V

The coating or lining being flexible and adapted to be stretched will readily follow the shaping or patterning of the mold or form, and therefore will not interfere with, the imparting of the mold or form pattern to the molded concrete. 7

It is found that theconcrete surface so obtained is highly moistureproof, is very hard and will therefore stand a lot of wear, is weather resisting and further is very easily washed in the same manner as glazed til orporcelain enamel. 4 While the invention is particularly adapted for use with cement, I hav found that a glazed or shiny finish may be obtained with other hardening materials such as "plaster of Paris.

It has been found that molds of plaster of Paris, whichhave had surfaces P p ed in this manner, may be used for molding concrete without the necessity of'using soap, oil or other coatings usually employed to pre vent adhesion of the concrete to-the mold. e I

It will .be seen that I have been able to produce a glossy or glaze finish without the addition of glazing materials and without the use of heat as is usually required in forming glazed surfaces and without a secondary or additional operation.

' What I claim as my invention is:

l. A method of forming a structure of an ordinary hydraulic cement concrete having a glossy or glazedface, which comprises placing said concrete in a form having a covering of hydrochloride of rubber; compacting the concrete to en'- sure intimate contact with said covering; allowing the covering to remain in contact with said concrete until the concrete has sufliciently hardened to obtain the desired height of gloss; and finally separating the covering from the hardened concrete.

2. For use in molding structures of cementitious material, a form having at least a portion of its molding surface formed of hydrochloride of rubber.

FRANCIS A. WILLIAMS. 

